A ship-in-a-bottle strategy to fabricate highly crystallized nanoporous graphitic C3N4 microspheres under pressurized conditions

Graphitic carbon nitride (g-C3N4) is a promising visible light photocatalyst but shows only moderate activity due to its high carrier recombination and low charge mobility. Herein, we synthesize a novel kind of nanoporous g-C3N4 microsphere (Np-CNM) with highly improved crystallinity via a ship-in-a-bottle strategy using mesoporous hollow silica spheres as nanoreactors. Confined thermal polymerization of the precursor inside the hollow cavity under pressurized conditions provide Np-CNMs with a highly nanoporous structure and improve crystallinity simultaneously which can not only significantly suppress the carrier recombination but also accelerate the interlayer charge transfer. The as-obtained Np-CNMs demonstrate a considerably enhanced photocatalytic hydrogen evolution rate (5785 mol(-1) h(-1) g(-1)) under visible-light irradiation ( 420 nm), which is more than 44 and 30 times that of bulk g-C3N4 and Np-CNMs produced at atmospheric pressure, respectively. This work identifies a reliable route to obtain highly crystallized nanostructured g-C3N4 microspheres, which are important for constructing high performance photocatalysts.